Simple Canvas Example

Simple Canvas Example — how to create a simple canvas.

Simple Canvas Example

Here's a complete example application that creates a GooCanvas with a rectangle and a text item in it:

  #include <stdlib.h>
  #include <goocanvas.h>
  
  
  static gboolean on_rect_button_press (GooCanvasItem  *view,
                                        GooCanvasItem  *target,
                                        GdkEventButton *event,
                                        gpointer        data);
  
  static gboolean on_delete_event      (GtkWidget      *window,
                                        GdkEvent       *event,
                                        gpointer        unused_data);
  
  
  int
  main (int argc, char *argv[])
  {
    GtkWidget *window, *scrolled_win, *canvas;
    GooCanvasItem *root, *rect_item, *text_item;
  
    /* Initialize GTK+. */
    gtk_set_locale ();
    gtk_init (&argc, &argv);
  
    /* Create the window and widgets. */
    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size (GTK_WINDOW (window), 640, 600);
    gtk_widget_show (window);
    g_signal_connect (window, "delete_event", (GtkSignalFunc) on_delete_event,
                      NULL);
  
    scrolled_win = gtk_scrolled_window_new (NULL, NULL);
    gtk_scrolled_window_set_shadow_type (GTK_SCROLLED_WINDOW (scrolled_win),
                                         GTK_SHADOW_IN);
    gtk_widget_show (scrolled_win);
    gtk_container_add (GTK_CONTAINER (window), scrolled_win);
  
    canvas = goo_canvas_new ();
    gtk_widget_set_size_request (canvas, 600, 450);
    goo_canvas_set_bounds (GOO_CANVAS (canvas), 0, 0, 1000, 1000);
    gtk_widget_show (canvas);
    gtk_container_add (GTK_CONTAINER (scrolled_win), canvas);
  
    root = goo_canvas_get_root_item (GOO_CANVAS (canvas));
  
    /* Add a few simple items. */
    rect_item = goo_canvas_rect_new (root, 100, 100, 400, 400,
                                     "line-width", 10.0,
                                     "radius-x", 20.0,
                                     "radius-y", 10.0,
                                     "stroke-color", "yellow",
                                     "fill-color", "red",
                                     NULL);
  
    text_item = goo_canvas_text_new (root, "Hello World", 300, 300, -1,
                                     GTK_ANCHOR_CENTER,
                                     "font", "Sans 24",
                                     NULL);
    goo_canvas_item_rotate (text_item, 45, 300, 300);
  
    /* Connect a signal handler for the rectangle item. */
    g_signal_connect (rect_item, "button_press_event",
                      (GtkSignalFunc) on_rect_button_press, NULL);
  
    /* Pass control to the GTK+ main event loop. */
    gtk_main ();
  
    return 0;
  }
  
  
  /* This handles button presses in item views. We simply output a message to
     the console. */
  static gboolean
  on_rect_button_press (GooCanvasItem  *item,
                        GooCanvasItem  *target,
                        GdkEventButton *event,
                        gpointer        data)
  {
    g_print ("rect item received button press event\n");
    return TRUE;
  }
  
  
  /* This is our handler for the "delete-event" signal of the window, which
     is emitted when the 'x' close button is clicked. We just exit here. */
  static gboolean
  on_delete_event (GtkWidget *window,
                   GdkEvent  *event,
                   gpointer   unused_data)
  {
    exit (0);
  }